Four crude oils (Prudhoe Bay, Norman Wells, Atkinson Point, and Lost Horse Hill) of different chemical composition were tested as to their biodegradability under mesophilic and psychrophilic conditions. Changes in bacterial numbers and chemical composition of the oils were monitored using a plate count and chromatographic technique respectively. Populations induced under psychrophilic conditions readily metabolized similar quality oils under mesophilic conditions. Mesophilic populations, however, only showed a limited metabolic capability on similar quality oils under psychrophilic conditions. Gram-negative rods were predominant in all the populations obtained under these experimental conditions. The ability of the mixed populations to use crude oil as a sole carbon source was dependent not only on the composition and amount of the n-saturate fraction but also on that of the asphaltene and NSO (i.e. nitrogen-, sulfur-, and oxygen-containing) fraction. Growth on an oil which lacked a normal n-alkane component indicated that the aromatic fraction of oil was capable of sustaining bacterial growth. Oil quality and temperature of incubation affected the generic composition of populations obtained which would use crude oil. The isoprenoids, phytane and pristane, while readily used under mesophilic conditions, were more resistant to bacterial metabolism under psychrophilic conditions.
The utilization of two crude oil samples of different quality at 4 and 30 C has been studied by using pure and mixed bacterial cultures obtained by enrichment procedures. Growth, emulsification, and utilization occurred readily at both temperatures. The crude oil residue is increased in specific gravity and readily sediments out of solution. A comparison of the chemical analysis of the oils by liquid and gas-liquid chromatographic procedures before and after growth showed that the n-saturate fraction had been preferentially used. Some utilization of the aromatic fraction also occurred. Enrichments obtained with a high-quality crude oil were not as effective in utilizing a lower quality crude oil as sole carbon source as a population enriched on the low-quality crude oil.
Replicate field plots comprising a control; control plus oil; control plus oil and fertilizer (urea phosphate, 27:27:0); control plus oil and bacteria; and control plus oil, fertilizer, and bacteria were established at Norman Wells, N.W.T., Canada. Plots were monitored over a 3-year period for changes in microbial numbers and the chemical composition of recovered oil. Where fertilizer was applied, there was a rapid increase in bacterial numbers, but no increase in fungal propagules. This was followed by a rapid disappearance of n-alkanes, isoprenoids, and a continuous loss in weight of saturate compounds in recovered oil. Changes in the content of asphaltenes, aromatics, and nitrogen-, sulphur-, and oxygen-containing fractions also are discussed. The seeding of oil-soaked plots with oil-degrading bacteria did not have any effect on the composition of recovered oil. Fertilized plots showed a more rapid rate of vegetation with cotton grass and Labrador tea being the dominant species in revegetation.
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